Touch tone phones (DTMF) were first deployed at scale in the US in 1963, but they would have been in development at the Bell System for quite a while before that. Possibly also some limited deployments. This ad from 1956 teases a future without rotary dials.
DTMF also led to the rise of Blue Boxes and Phreaking.
“We also provide customer service through our website where you can chat with an AI 24/7.”